3 y<> National Rivers Authority Anglian Region THE MANAGEMENT OF THE WATER RESOURCES OF THE LITTLE OUSE GROUNDWATER UNIT .V E n v ir o n m e n t A g e n c y NATIONAL INFORMATION ANGLIAN Kingfisher Ho Ort Peter J. A. Barker, Senior Engineer (Water Resources) D. Evans, Hater Resources Planning Engineer December 1993 DOCUMENT CONTROL SHEET Project: THE MANAGEMENT OF THE WATER RESOURCES OF THE LITTLE OUSE GROUNDWATER UNIT Title: FINAL REPORT File Ref: 657/3/5 & GW Unit 9 Document Approval and Amendment Record Version No.: 3 Status: Internal Report Only Author: Julie Barker Checked: David Evans Approved: Date: December 1993 Purpose and Distribution: To establish a water resources policy for the little Ouse Groundwater Unit for NRA Staff. Document History Previous Version Date Comments Number 1 Feb Consultation Draft 1993 2 August Sections about Great Ouse Groundwater 1993 Scheme changed. SUMMARY This report recommends a strategy for the management of the water resources of the Little Ouse groundwater unit. The Little Ouse groundwater unit covers parts of several river catchments, including those of the Little Ouse, Thet, Sapiston (Black Bourn) and Cut-Off Channel (see Figure 1). The current is sues in the Little Ouse catchment include; the increasing demand for water abstraction, the protection of wetlands, the protection of river levels and flows, the protection of river water quality and the future use and development of the Great Ouse Groundwater Scheme. This unit is part of the "Ely Ouse Catchment Management Plan". The water in the river system is derived in four ways; - rainfall runoff, predominately from areas of Boulder Clay cover in the upper part of the catchment, - baseflow from the Chalk aquifer, which underlies the whole catchment, and from minor sand and gravel deposits, - artifical augmentation using groundwater, and - effluent discharges. During the recent drought, the river flows were sustained by groundwater using the Great Ouse Groundwater Scheme and by effluent discharges. There are twenty three water dependent S . S . S. I. s in the unit and over fifty wetland Wildlife Trust sites. Part of the Little Ouse unit is included in the Breckland Environmentally Sensitive Area. The long term average available water resource is allocated firstly to meet environmental needs and secondly for abstraction purposes. It is shown that the water resources of the Little Ouse unit are fully committed. This conclusion is sensitive to the amount allocated to the river, which is provisional and requires further investigation. However, for the present, future applications for additional groundwater abstraction will not be recommended. Several options are examined to address the current issues in the unit. Recommendations are made for further studies. CONTENTS List of Figures and Tables : apart from a few Tables in the test all Figures and Tables are at the back of the report. PageJNo. 1. INTRODUCTION 1.1 Purpose of Report 1 1.2 Location 1 1.3 Sub-Unit Divisions 1 1.4 Current Issues 1 1.5 Ely Ouse Catchment Management Plan 2 DESCRIPTION 2.1 Geology and Hydrogeology 3 22 Hydrology 3 2.2.1 Gauging Stations 4 2.2.2 Current Metering 5 23.2 Great Ouse Resource Model 6 WATER RESOURCES 3.1 Surface Water Resources 8 3.2 Groundwater Resources 8 3.2.1 Cambridge Water Plan (1985) Assessment of Resources 8 3.2.2 Current Assessment of Resources 9 4. WATER QUALITY 4.1 Surface Water 11 4.2 Groundwater 12 5. WATER USE IN THE CATCHMENT 5.1 Public Water Supply 13 5.1.1 PWS Abstractions 13 5.1.2 Public Water Supply Transfers into and out of the Catchment 14 5.13 Public Water Supply : Return of Effluents 14 5.1.4 Public Water Supply : Proposed Developments 15 5.2 Private Water Undertaking 15 5.3 Agriculture 15 5.4 Industry 16 55 Raw Water Transfer: The Great Ouse Groundwater Scheme 16 5.5.1 The Great Ouse Groundwater Scheme Boreholes 16 5.5.2 The transfer at Hockwold 17 5.6 Environmental Water Needs 18 5.6.1 Wetland SSSIs and Other Sites of Conservation Interest 18 5.6.2 Cut-Off Channel 18 5.6.3 In River Needs 5.6.4 Breckland Environmentally Sensitive Area 20 5.7 Navigation 20 5.8 Fisheries 21 6. BALANCE OF RESOURCES AND DEMANDS 6.1 Whole Catchment 22 6.2 Sub-Units 23 6.3 Allocation of Little Ouse Groundwater Resources 24 6.4 Balance including the Great Ouse Groundwater Scheme 24 7. ISSUES AND OPTIONS 7.1 The Increasing Demand for Water Abstraction 25 7.1.1 Increasing Demand for Direct Water Use 25 7.1.2 Increasing Demand for Public Supply 25 7.13 Demands Beyond the little Ouse Catchment 26 12 The Environmental Needs for Water 26 7.2.1 River Needs - Fluvial Rivers 26 7.2.2 River Needs - the Fen River 26 7 2 3 Wetland Needs 26 73 River Water Quality 27 7.4 Future Management of the Great Ouse Groundwater Scheme 28 7.4.1 The Net Gain of the Scheme 28 7.4.2 licensed Quantities for River Support 28 7.43 The "Cambridge Reduction" 30 7.5 Licensing Policy 30 8. CONCLUSIONS 8.1 Geology and Hydrogeology 32 8 2 Hydrology 32 83 Groundwater Resources 32 8.4 Water Quality 32 8.5 Water Abstraction 32 8.6 Environmental Water Needs 32 8.7 Navigation 33 8.8 Fisheries 33 8.9 Water Resources and Demands 33 8.10 Future Management of the Great Ouse Groundwater Scheme 33 RECOMMENDATIONS 9.1 Interim Licensing Policy 34 9.2 Further Investigations 35 References 37 Figures Appendix 1 : Details of SSSI sites and Wildlife Trust Sites 81 LIST OF FIGURES Page Title 1 38 The Little Ouse Catchment 2 39 Sub Units defined for Little Ouse 3 40 Geology 4 42 Chalk Groundwater Levels April 1988 5 43 Chalk Groundwater Levels September 1991 6 44 Gauging Stations and Current Metering Sites 7 45 Flow Duration Curve Knettishall 8 46 Flow Duration Curve Euston County Bride 9 47 Flow Duration Curve Abbey Heath 10 48 Flow Duration Curve Stonebridge 11 49 Flow Duration Curve Quidenham 12 50 Flow Duration Curve Redbridge 13 51 Flow Duration Curve Bridgham 14 52 Flow Duration Curve Melford Bridge 15 53 Flow Duration Curve Rectory Bridge 16 54 Abbey Heath Gauging Station 17 57 River Quality Classification 18 61 Discharge Consents greater than 100m3/d 19 65 History of Groundwater Abstraction 20 66 Public Water Supply Borehole Sources 21 73 The Great Ouse Groundwater Scheme 22 74 The Great Ouse Groundwater Scheme 23 75 Wetland Sites of Special Scientific Interest and Wetland Wildlife Trust Sites 24 76 East Wretham Heath SSSI 25 77 Schematic Map of the Little Ouse 26 78 Thet Groundwater Sub Unit : 7 day Flow Duration Curves 27 79 Upper Little Ouse Sub Unit : 7 day Flow Duration Curves 28 80 Sapiston Sub Unit: 7 day Flow Duration Curves LIST OF TABLES No. Page Title 1 41 Water Level Data 2 5 Flow Measurements in the Little Ouse Unit 3 6 Current Metering Sites 4 9 Little Ouse Resources : 1985 Calculations 5 9 Areas of Geology 6 10 Rainfall Analysis 7 10 Little Ouse Resources - 1993 Calculations 8 55 River Quality Objectives 9 56 National Water Council River Quality Classification 10 58 Discharges Made to the Little Ouse System 11a 62 History Licensed Groundwater Abstraction 1966-1993 lib 63 Licensed Quantities for Sub Units A, B, C and D 1993 12 13 Public Water Supply Licence Details 13 15 Proposed Public Water Supply Developments in the Unit 14 64 Current Abstraction Applications in the Little Ouse Unit 15 67 The Great Ouse Groundwater Development Boreholes 16 20 River Allocation 17 22 Balance of Resources and Demands : Whole Unit 18 23 Balance of Resources and Demands per Sub-Unit 19 24 Allocation of Groundwater Resource 20 29 Required River Support Pumping Capacities - tcmd 21 29 Required 600 day River Support licensed Quantities - tcm 22 30 Potential Changes to the Great Ouse Groundwater Scheme licences WATER RESOURCES OF THE LITTLE OUSE GROUNDWATER UNIT 1. INTRODUCTION 1.1 Purpose of Report The purpose of this report is to review the water resources of the Little Ouse Groundwater Unit. In particular how the water resources are currently used and managed, to identify the future needs both environmental and human, and to make recommendations to optimise future water resource management in this unit. 1.2 Location Figure 1 shows the area of the Little Ouse Groundwater Unit (Unit 9). The western boundary has been defined by the base of the Tottemhoe Stone horizon within the Lower Chalk. The remaining boundaries are groundwater divides derived from the minimum groundwater heads shown on the "Hydrogeological map of Northern East Anglia" (1976) and the "Hydrogeological map of Southern East Anglia" (1981). The Unit covers all or part of the following surface water catchments; the River Thet (6/33/44), the Little Ouse (6/33/42, 6/33/43, 6/33/45 and 6/33/46), the Sapiston (6/33/41), the River Lark (6/33/37 and 6/33/39), the Cut Off Channel (6/33/56), the River Wissey (6/33/48), the River Waveney (7/34/16) and small parts of the River Tiffey (7/34/13) and the River Gipping (7/35/8) and a tributary of the Yare (7/34/13). 13 Sub-unit divisions The unit has been divided into four sub units in order to examine the utilisation of water resources in more detail. The divisions were made with regard to surface hydrology and groundwater flows.